Electric furnace.



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Winnaars. snare or urac-ana reines, un

cana-sins coureur, or new Yom, n.

ELECTRC FURNACE.

' the following 1s a specitication.

` tors of opposing phase; and

ic furnaces late certain My invention relates to elect and has for its object to obv diliculties-in the operation of such furnaces, and to provide an improved system of current delivery to such furnaces, whereby electrical losses are minimized, a high power factoicbtained, and uniformity in power consumption maintained.

In my prior Patents 77h25() and 757,6l8, .l have described the application ot multiphase currents to a furnace having a single hearth provided With a large number of electrodes. The present invention is an improvement on the systems of current distribution described in these prior patents, and consists, in addition to dividing the vcurrent supply to the furnace into many phases, in further sub-dividing the current in each phase into several portions each carried by its oWn conductor; in so arranging these conductors that each current portion is supplied to the corresponding electrode by -diiferent routes, along which flow currents of opposing sign; and in the particular arrangement of the conductors which deliver current from the bus-bars to the electrodes.

As a result of these improved arrangements, the self-induced voltage of the system, as a Whole, is reduced because (l) the induction which Would result't'rom the pas? sage of a large Acurrent through a small number of electrodes is diminished by the use of a large number of electrodes; (2 the induction is further diminished by using a multiplicity of conductors to each ele'ctrode, thereby lessening the amperage which has to be carried by any single conductor; (3) the induction is still further diminished by arranging these multiple conductors in such relation that each conductor is', as far as possible, surrounded by return conduc- (Ll) by so arranging the conductors leading from the bus-bars to the electrodes as to minimise the induction at this point.

Snecma-ation of Letters Patent.

.implication led January 21, 1914,.

nace, preferably circular Patented Serial No. $23,534.

in the accompanying diagram, A represents 'the hearth of a six-phase electric fur'- l shape, and having siX electrodes, l, lil, .l l, EV, V, Vl.

T is a three-phase transformer having its secondary circuits connected tolbus-bars, l, 2, 3, d, 5, 6, leading to the furnace. The transformer vis -of the three-phase double delta type, with its primary coils 7, 8, 9, connected as shown to the circuit l0, and its second-aries 7l, 72, 81,182, and 91, 92, con- 'nected to the bus-bars as shown.

Above the furnace are conductors arranged, as shown, in two deltas, one above the other, and constituting', in effect, tivo distincttsystems connected only Within the furnace by acting upon the common resistance there. The electrodes are connected to the bars of these deltas by cables s, c, c.

he course of the current along the sets of bars 1, 2, 3, 4, 5, 6, can readily be rolloived by the arrows which are made long or short to represent the phase amplitude, Ithe barbs indicating the direction of the current. The inductive reactions which Will take place between adjacent bars will also be readily apparent.

lt will be noted that ceives current from ample, electrode H receives current from the b r'\ delta, and from the third bar 2, extending directly to the transformer on the righthand side; while the opposite electrode V receives current from two bars 5, 5, on the right-hand by Way or" the upper delta and from a third conductor connected directly to the transformer on the left-hand side. By this arrangement, the mutual inductance between the sets of bus-bars on both the right and left-hand sides can be largely neutralized.

lt will be noted that the circuit connections in each delta are also arranged to minimize the self-induced voltage as far as possible, thus at the point Q in the lower elta, the 2-bar will be carrying one-third ot the total current which is delivered through the electrode H While the 4-bar will be carrying current flowing in the same direction only one-sixth as large as the total current, since the return of the current deliveredto the furnace thrcu'rh each electrode rethree sources, for exhe electrode y leading to each electrode, 2o

H, is divided between the electrodes 1V and Vl. The total self-induced voltage at this point is, therefore, only one-halt` of that which would be produced if a single conductor were carrying the' total quantity of current. A similar condition would exist' at the point R on the second leg of the delta, while at the point Z on the third leg whatever currents might he flowing in the two :onductors would be in opposite directions and the induction therein would, he neutralized. The total unneutralized induction would therefore, be that produced along the delta-shaped bars plus that in the short cables leading from these bars trode.1 For example, with a current of 10,000 aniperes at 60 cycles, there would he a self-induced Vvoltage ot' about one volt per foot ir the cables, but only one-half volt'per f it' along the legs of theY delta. The induction in the bus-bars, interlaced in the manner shown, is practically negligible.

While l have shown' three conductors it is obvious that the principle of dividing and subdividing' the amperes and causing each portion of the current to arrive at-the cables by different foutes can be extended, and the inductive eil'ects be, in this manner, still further reduced. lt is also obvious that the saine principle can loe applied to furnaces having .a smaller number of electrodes, and a V ,plicity sn llernurnber of conductors carrying current to each electrode.

claim l. 'An electric furnace having a multiof electrodes, means for supplying inultiphase currents thereto, each ol said electrodes receiving current of different phase l'roni that of neighboring electrodes and by different routes 'from the source of current, each route being interlinked with others carrying currents of opposing phase.

2. An electric furnace having a ninltiplicity of symmetrically disposed electrodes, means for supplying multipliase currents thereto, each o said electrodes receiving currentof different phase from that of neighboring electrodes and by diiierent vroutes from the source of current, each route being interliuned withi'others carrying currents ci' opposing phasr-g.

3. An electric. furnace having a plurality of electrodes, means for supplyingyiniultiphase currents thereto comprising alf plurality .nl conductors in parallel for" each phase leading to said electrodes.the conductors for cach electrode extending thereto by different routes, eachroute being interlinlied with others carr 'm0' current of o posing phase, whereby the Aself-inductionfof 6. An electric furnace having a plurality of sets of electrodes,

three electrodes in each set, means for independently supplying 3-phase current to each set, said means comprising a plurality of conductors in each phase, all the conductors leading from the vsources of supply to the urnacebeing interlinked with others carrying current o-op posing phase.

7. An electric furnace having a plurality of sets of electrodes, three electrodes in each set, means for independently supplying 8phase current to each set, said means coinprising a plurality of conductors in each phase and delta-connected to the electrodes, the conductors for each delta being interlaced with opposing phase current-carrying conductors of another delta.

ln testimony whereof, l aliix my signature in presence of two witnesses.

WILLIAM SMITH HURRY.

.l/Vitnesses z SIDNEY Oris, GEO. R. JUDD. 

